1. Field of the Invention
The invention relates to electric motors and is directed more particularly to an electric motor having brush tubes fixed in an endframe portion of the motor.
2. Description of the Prior Art
In electric motors, brushes are commonly retained in brush tubes which usually are molded integrally with a plastic endframe portion of the motor. The endframe and brush tubes typically are of a plastic material. The brush tubes are square in cross-section and hollow, somewhat like elevator shafts, in which spring-biased brushes are slidably moveable into engagement with the commutator of the motor.
In assembly of such motors, it is common that a coil spring is inserted in a brush tube and, thereafter, a brush, with a shunt attached thereto, is inserted in the brush tube on top of the spring. In shipment and handling prior to assembly, it is sometimes the case that the brush and spring fall out of the open end of the tube. At the final assembly point, it is on occasion overlooked that the spring is missing. It is usually apparent when the brush is missing, but sometimes the brush is replaced without the absence of the spring having been noticed. In some instances, the shunt may, for a limited time, exercise spring-like properties and hold the brush in a commutator-engaging position. However, the shunt usually cannot maintain its spring-like performance and, in due course, the brush falls away from commutator engagement, terminating proper operation of the motor.
Accordingly, there exists a need for a motor having brush spring retention means.